Related Clues:

• Pollen, e.g.
• Dust, for one
• Bee venom is one
• Dust or pollen, e.g.
• Sneeze-causing substance
• Any substance that causes a hypersensitive reaction
• 100% green product may cause unhealthy reaction
• Work in a particular key can cause an abnormal reaction
• Right to enter claim with name which provokes a reaction
• Something creating reaction for entirely green design
• Protein making everyone turn green
• One provokes a reaction in footballer, generally
• Wheat, say, somewhat smaller, generally
• Go across the Channel with information that may produce adverse reaction
• Line in general not normally something to get a reaction